I have a girl that absolutely loves Marquise diamonds. We have been talking about getting engaged and her mom really wants me to just replace the diamond in her grandmothers engagement ring. Which i am fine with and she loves her grandmothers ring anyway. My trouble is i know nothing about diamonds and whats good or bad. I have read through a lot on the information here and it makes my head spin. Any advice on where to go and look for a diamond would be greatly appreciated.